Average Equivalence Ratio Research Articles

Effects of Scavenging-Port Semi-Direct Injection Strategy on Mixture Formation for a Two-stroke Spark Ignition Kerosene Piston Engine

Abstract The two-stroke spark ignition (SI) kerosene piston engines (KPE) are commonly utilized in lightweight unmanned aerial vehicles (UAV). The quality of mixture formation is crucial for the engine performance. This paper investigates the mixture quality in a semi-direct injection (SDI) SI KPE. Computational models were established using a 1D simulation tool and a 3D computational platform to analyze the effects of injection pressure, injection timing, and fuel temperature on atomization and mixture formation. The results indicate that increasing injection pressure promotes a more uniform mixture distribution. Higher injection pressures also enhance the formation of fuel film. At the top dead center (TDC), the average equivalence ratio (ER) with an injection pressure of 0.7 MPa is 3.8% higher than that of 0.3 MPa and 1.9% lower than that of 0.5 MPa. Delaying the injection timing increases the pressure difference between the cylinder and scavenging port, weakening fuel penetration and improving the fuel gasification rate. When the injection timing is set to 180 °CA ATDC, the average ER at TDC is 10.4% higher than that at 140 °CA ATDC, with a 6.6% decrease in fuel capture rate. Increasing fuel temperature effectively enhances the fuel gasification rate. However, excessively higher fuel temperatures will not significantly improve mixture quality. At a fuel temperature of 380 K, the average ER at TDC is 2.9% higher than that at 340 K. Response surface analysis reveals that the control parameters affect the average ERs in the following order of influence: injection timing, fuel temperature, and injection pressure. This study provides theoretical support for optimizing control parameters in SDI SI KPEs.

Effect of injection pressure on low-temperature fuel atomization characteristics of diesel engines under cold start conditions

Exploring the atomization characteristics and spray impingement characteristics of low-temperature fuel under different injection pressures has important practical significance for improving the cold start performance of diesel engines. In this study, based on LIEF-PIV combined laser testing technology, a fuel atomization experimental system for diesel engine cold start was established. The concentration and velocity fields of low-temperature fuel with the temperature from 20 to - 40 ℃ were experimentally analyzed within the injection pressures of 40-80MPa. The results showed that the increase of injection pressure increased the initial kinetic energy of the diesel droplets, whereas the concentration gradient of spray decreased significantly. Meanwhile, the mixing effect of spray and ambient gas increased. When the fuel temperature decreased from 0 ℃ to - 20 ℃, the values of the average equivalence ratio in the near-wall region decreased from 0.52 to 0.21. The change of injection pressure had an obvious effect on the macro morphology of wall-impinging spray and the flow characteristics of the fuel/air mixture. When the injection pressure increased from 40MPa to 80MPa, the difference of maximum turbulent kinetic energy among various temperatures increased from 0.66 m2/s2 to 0.90 m2/s2.

A detailed multidimensional simulation for the cold start process of a gasoline direct injection engine using a fractal engine simulation model

The cold start process for a gasoline direct injection (GDI) engine was studied through multidimensional simulations using a Fractal Engine Simulation (FES) model integrated into CONVERGE CFD. The simulations were focused on the very first firing cycle in the cold start process, as most of the hydrocarbon emissions derive from this cycle. The dramatically changing engine speed and low wall temperatures in the cylinder present challenges for simulation. It turned out that the FES model was able to predict the in-cylinder pressure traces for all four cylinders for the first firing cycle, and gave good agreement with the experimental measurements under these extremely transient conditions. More comprehensive analysis demonstrated the causes for the different behavior of the combustion in different cylinders: more injected fuel and a higher induced tumble ratio in cylinder 3, the first to fire, led to a higher average equivalence ratio and better fuel distribution, which resulted in the highest peak pressure; the worse fuel distribution from the lower tumble ratio, together with the lower normalized turbulence, caused weaker combustion in cylinder 4; the peak pressures were similar and on the low side for cylinders 2 and 1, mainly determined by the low average equivalence ratio. An improved strategy with multiple injections was proposed, with the first two in the intake stroke and two later injections in the compression stroke rather than one injection during each stroke. Although the total injected fuel was the same as the baseline strategy, more fuel evaporated due to the enhanced fuel evaporation from both droplets and wall films, resulting in a higher average equivalence ratio in the cylinder. The peak cylinder pressure and IMEP rose by 33.3% and 8.4%, respectively, using the 4-injection strategy compared to the baseline 2-injection strategy, and the 4-injection strategy was verified by the experiments, as well.

A parametric study to improve first firing cycle emissions of a gasoline direct injection engine during cold start

A parametric study was carried out for the first firing cycle of a 4-cylinder, 2.0-liter, turbocharged gasoline direct injection (GDI) engine. The primary goal was to see how changes in the fuel injection parameters would affect the GDI engine combustion and emissions for the first four combustion events that constitute the first firing cycle. Experimental studies were carried out with a custom-designed powertrain control system to measure the HC emissions and pressure development for the first firing cycle. The quantitative experimental results were accompanied by simulations of the detailed temporal and spatial fuel concentration profiles using Converge CFD engine simulation software. An alternative calculation method was used to calculate the average combustion equivalence ratio for each of the four cylinders. This method showed that the majority of the cold start HC emissions during the first firing cycle was unburned gasoline and its possible decomposition products, which did not contribute significantly to the combustion and heat release. For the same amount of fuel injected into a cylinder, increased fuel rail pressure resulted in better evaporation and combustion, while slightly increasing the HC emissions during the cold start process. A multiple injection strategy was studied that split the fuel delivery between the intake stroke and the compression stroke with either one or two injections in each of those strokes (two or four injections total). The quadruple injection strategy led to better first cycle combustion, with higher engine IMEP and lower HC emissions. This resulted from a richer fuel mixture in the region near the spark plug due to better fuel evaporation and a better spatial fuel distribution. While increasing fuel rail pressure with either injection strategy failed to significantly lower the HC emissions given the same amount of injected fuel mass, higher rail pressure with the quadruple injection strategy resulted in higher IMEP for the same amount of injected fuel; this may provide the possibility to reduce the total fuel injection mass which may have benefits for both fuel consumption and emissions.

Detailed chemistry modeling of rotating detonations with dilute n-heptane sprays and preheated air

Utilization of liquid fuels is crucial to enabling commercialization of rotating detonation engines (RDE) in the near future. In this study, Eulerian-Lagrangian simulations are conducted for rotating detonative combustion with dilute n-heptane sprays and preheated air. Two-dimensional flattened configuration is used and a skeletal chemical mechanism with 44 species and 112 elementary reactions for n-heptane combustion is adopted. The flow structure, droplet distribution, and thermochemical parameters in the refill zone are first analyzed. It is shown that the mixture in the refill zone is heterogeneous, including evaporating droplets, vapor, and air. When the total temperature is below 950 K, the average equivalence ratio increases with the total temperature. When it is higher than 950 K, the average equivalence ratio is almost constant. Subsequently, the chemical explosive mode analysis is applied to identify the controlling reactions and dominant combustion modes in the fuel refill zone and reaction fronts. Results demonstrate that the initiation reaction (R104: n-C7H16 + O2→ 2-C7H15 + HO2) and low-temperature reaction (R107: RO2→ R'O2H) are dominant in the upstream and downstream of the refill zone, respectively. The intermediate species from low-temperature chemistry, R'O2H, is found to be important for the chemical explosive mode in the undetonated mixture. The influence of species diffusion and dispersed droplets is further analyzed. Results show that vapor autoignition facilitated by droplet evaporation occurs in the refill zone. Finally, the effects of the air total temperature on the detonation propagation speed and RDE propulsion performance are investigated. It is found that the detonation propagation speed and specific impulse increase with air total temperature. The total pressure ratio first increases and then decreases as the air total temperature increases. Moreover, when the total temperature of the preheated air is above 1,300 K, the effects of low-temperature chemistry are negligible.

Development of semi-empirical soot emission model for a CI engine

Soot is one of the main harmful emissions of diesel engines that is mainly generated in the reacting fuel jet of diesel injection. Over 99% of the engine-out soot can be filtered by a diesel particulate filter (DPF). However, when the soot load of the DPF is high, a regeneration process that oxidizes the accumulated soot reduces fuel economy. A real-time soot estimation model can contribute to real-time feedback soot control under transient conditions to minimize the engine-out soot emission and frequency of DPF regeneration.A zero-dimensional engine-out soot estimation model for a diesel engine is developed in this study. The semi-empirical soot model considers both the formation and oxidation of soot. In the model, soot formation was correlated with the cross-sectional average equivalence ratio at the lift-off length of the fuel spray. The equivalence ratio at the lift-off length is an indicator of how much air and vaporized fuel are mixed as the fuel reaches the reaction zone. The mass of the injected fuel and combustion duration were also correlated with soot formation. The Nagle and Strickland-Constable mechanism, which calculates the soot oxidation rate was correlated with the soot oxidation in this study. The results of the soot estimation showed an R2 of 0.901 and root mean square error of 10.8 mg/m3 for steady-state experimental cases. The engine-out soot model was also combined with the in-cylinder pressure model proposed by the authors, and validated through the transient Worldwide Harmonized Light Vehicles Test Cycle (WLTC) mode. The estimates agreed with the measured soot, with an accumulated soot error of approximately 6% during the WLTC, even without using an in-cylinder pressure sensor. The soot model developed in this study can help minimize tailpipe-out soot emissions and improve fuel economy by influencing the real-time feedback control during transient and frequent DPF regeneration.

Simulations of rotating detonation combustion with in-situ evaporating bi-disperse n-heptane sprays

Eulerian-Lagrangian simulations are conducted for two-dimensional Rotating Detonative Combustion fueled by bi-disperse n-heptane sprays without any fuel pre-vaporization. Parametric studies are performed to study the influences of droplet diameter and droplet distribution on the rotating detonation wave. The extinction process of the detonation wave is also been analyzed. It is found that small n-heptane droplets (e.g., 2 µm) are completely vaporized in the fuel refilling area. Increasing the droplet diameter causes the droplet to fail to evaporate completely within the fuel refilling area and exist after the detonation wave. A reflected shock can be observed after the detonation wave. When the droplet diameter is larger than 10 μm, the higher pressure after the detonation wave leads to the reactants cannot be sprayed into the combustor, eventually leading to extinction of the detonation wave. In bi-disperse n-heptane sprays, presence of droplets with small diameter stabilizes the detonation wave. The average equivalence ratio (up to 0.66 only) in the fuel refilling area is lower than total equivalence ratio (1.0 in this work), and the average equivalence ratio decreases with increased droplet diameter in the bi-disperse n-heptane sprays. The increase in droplet diameter decreases the detonated fuel fraction and detonation wave speed. The detonation speeds in bi-disperse n-heptane sprays are 3–9% lower than the respective gaseous cases. Moreover, the results also show that propulsion performance of rotating detonation combustor, such as thrust and specific impulse, decreases with the droplet diameter.

The quantitative characterization of the ignition process for a lean staged injector: Influence of the air split between pilot swirlers

The ignition of a lean staged injector aimed at aeronautical application is a transient and complex phenomenon, which involves fluid dynamics, turbulent mixing, chemical kinetics, as well as their mutual interactions. In the present research, a staged injector, designed based on stratified partially premixed combustion concept, is introduced. The ignition performance of stratified partially premixed injectors with different air split ratios between pilot swirlers are experimentally acquired, which exhibits apparent distinctions. In order to make quantitative analyses, the classical physical ignition model is improved, in which the flame propagation process is further divided into the axial and radial propagation sub-processes. Nonreacting flow field and discrete phase simulations, validated by experiment results, are utilized to obtain the velocity and spray distributions. Physical parameters characterizing the ignition sub-processes are defined and calculated based on the numerical simulation results. Conclusions are made by comparing the physical parameters of the ignition sub-processes. The radial propagation of the ignition kernel is responsible for the ignition performance difference between the two injectors with different pilot air split ratios (PASR) in that the average equivalence ratio along the radial propagation route of PASR = 7:3 is one order richer than that of PASR = 2:8. The present ignition analysis and model can be further extended and developed for the optimization of ignition performance of lean staged injector.

Experimental research on the effect of reflected shock waves on the evolution of a high-pressure diesel spray

The shock wave has become a common phenomenon in modern diesel engines with the continuous increase in the fuel injection pressure. The shock wave reflects in the cylinder and affects the macroscopic structure of the spray and the mixing effect between the spray and surrounding air. In this study, the effects of the reflected shock wave on the evolution characteristics and the mixing characteristics of a high-pressure diesel spray were investigated using the Schlieren imaging method. The results show that the reflected shock wave significantly suppresses the development of the spray in the radial direction. However, the reflected shock wave has little effect on the development of the spray tip penetration. The volume and the average equivalence ratio of the spray under the reflected shock wave are also lower than those without the reflected shock wave. In addition, the evolution of the spray under different fuel injection angles was also analyzed. The results show that the different fuel injection angle affects the development of the spray width in the radial direction, which in turn has a significant influence on the spray cone angle.

LPG 증기보일러의 배기 배출물에 미치는 요소-SCR 후처리 시스템의 영향에 관한 연구

The aim of this study is to investigate the effect of SCR reactor on the exhaust emissions characteristics in order to develop a urea-SCR aftertreatment system for reducing <TEX>$NO_x$</TEX> emissions. The experiments are conducted by using a flue tube LPG steam boiler with the urea-SCR aftertreatment system. The urea-SCR aftertreatment system utilizes the ammonia converted from 17% aqueous urea solution injected in front of SCR catalyst as a reducing agent for reducing <TEX>$NO_x$</TEX> emissions. The equivalence ratio, urea injection amount, ammonia slip and <TEX>$NO_x$</TEX> conversion efficiency relative to boiler load are applied to discuss the experimental results. In this experiment, the average equivalence ratio is calculated by changing only the fuel consumption rate while the intake air amount is constantly fixed at <TEX>$25,957.11cm^3/sec$</TEX>. The average equivalence ratios are 1.38, 1.11, 0.81 and 0.57 when boiler loads are 100, 80, 60 and 40%. The <TEX>$NO_x$</TEX> conversion efficiency is raised with increasing urea injection amount, and <TEX>$NH_3$</TEX> slip is also boosted at the same time. Consequently, the <TEX>$NO_x$</TEX> conversion efficiency relative to boiler load should be examined in combination with urea injection amount and <TEX>$NH_3$</TEX> slip. The results are calculated by 89, 85, 77 and 79% for the boiler loads of 100, 80, 60 and 40%. The appropriate amount of urea injection for the respective boiler load can be not discussed by only <TEX>$NO_x$</TEX> emissions, and should be determined by considering the <TEX>$NO_x$</TEX> conversion efficiency, <TEX>$NH_3$</TEX> slip and reactive activation temperature simultaneously. In this study, the urea amounts of 230, 235, 233 and 231 mg/min are injected at the boiler loads of 100, 80, 60 and 40%, and the final <TEX>$NH_3$</TEX> slips are measured by 8.48, 5.58, 11.97 and 11.34 ppm at the same conditions. THC emission is affected by the SCR reactor under other experimental conditions except 100% engine load, and CO emission at only 40% engine load. The rest of exhaust emissions are not affected by the SCR reactor under all experimental conditions.

An investigation of the impact of injection strategy and biodiesel on engine NOx and particulate matter emissions with a common-rail turbocharged DI diesel engine

An investigation of the impact of engine injection strategy on NOx and particulate matter (PM) emissions with biodiesel fueling was conducted with a common-rail turbocharged direct injection diesel engine at moderate speed and different load/torque conditions. The fuels included a baseline ultra low sulfur diesel fuel (ULSD) and a B40 (v/v) blend of a soybean methyl ester (SME)-based biodiesel and ULSD. Single fuel injections at start of injection timings over a range from 9° before to 3° after top dead center with different fuel injection pressures were investigated. It is found that at all load conditions, an increase of fuel injection pressure significantly increases NOx emissions, and that with the same injection strategy as the baseline diesel, biodiesel fueling increases NOx emissions. For particulate matter emissions, it is found that an increase of fuel injection pressure decreases PM emissions for all load conditions. Meanwhile, biodiesel fueling has a more significant effect on PM emissions at low load and a less significant effect at moderate to high load. For an engine running with early SOI (highest brake fuel conversion efficiency in this work), a decrease of fuel injection pressure can counter the biodiesel NOx effect while maintaining a similar or even lower level of PM emissions as ULSD. Both biodiesel fueling and the change of fuel injection pressure did not significantly affect the brake fuel conversion efficiency, but retarding the start of injection appears to decrease it. Apparent heat release analysis shows a faster and higher heat release peak with higher fuel injection pressure. With biodiesel fueling, an earlier of start of combustion can be observed for low load, but no significant difference in combustion phasing can be observed at moderate to high loads. A fuel spray, mixture stoichiometry field and lift-off length model was employed. Linear correlations between the average oxygen equivalence ratio of the fuel–air mixture at the autoignition zone near the lift-off length and brake specific NOx emissions were observed for all load conditions, regardless of fuel type. This confirms that the dominant factor that determines NOx emissions is the ignition event controlled by the oxygen equivalence ratio at the autoignition zone.

Effects of Rail Pressure, Pilot Scheduling and EGR Rate on Combustion and Emissions in Conventional and PCCI Diesel Engines

In Diesel engines the optimization of engine-out emissions, combustion noise and fuel consumption requires the experimental investigation of the effects of different injection strategies as well as of a large number of engine operating variables, such as scheduling of pilot and after pulses, rail pressure, EGR rate and swirl level. Due to the high number of testing conditions involved full factorial approaches are not viable, whereas Design of Experiment techniques have demonstrated to be a valid methodology. However, the results obtained with such techniques require a subsequent critical analysis, so as to investigate the cause and effect relationships between the set of engine operating variables and the combustion process characteristics that affect pollutant formation, noise of combustion and engine efficiency. To this purpose, the zero-dimensional multizone diagnostic combustion model developed at ICEAL was applied for the combustion and emission formation analysis in two different diesel engines, for various sets of injection strategies and engine operating parameters. The experimental data were acquired at the highly dynamic test rig of ICEAL, both in a EURO V low compression ratio diesel engine with a twin-stage turbocharger, equipped with piezoelectric injectors, and in a PCCI low compression ratio diesel engine equipped with solenoid injectors. The model results were discussed and reported in the well known ϕ-T diagrams, which give a synthetic representation of the local thermodynamic charge conditions during the mixture formation and premixed diffusion combustion processes. The rail pressure increase was found to be an effective means to improve fuel-charge premixing and to lower the average local equivalence ratio of the charge during premixed combustion, so leading to a decrease in soot formation. As regards the effects of cooled high-pressure EGR on combustion, it was shown that an increase of its rate does not significantly affect the average equivalence ratio during premixed combustion, which is associated to the soot formation rate. Finally, a proper calibration of the dwell-time between pilot and main injection, so as to have the main injection pulse center-of-gravity phased in correspondence to the start of pilot burning, resulted to produce a reduction of CO and soot emissions higher than 50% with respect to baseline case, without any deterioration of NOx emissions

Experimental annular stratified flames characterisation stabilised by weak swirl

A burner for the investigation of lean stratified premixed flames propagating in intense isotropic turbulence has been developed. Lean pre-mixtures of methane at different equivalence ratios were divided between two concentric co-flows to obtain annular stratification. Turbulence generators were used to control the level of turbulence intensity in the oncoming flow. A third annular weakly swirling airflow provided the flame stabilisation mechanism. A fundamental characteristic was that flame stabilisation did not rely on flow recirculation. The flames were maintained at a position where the local mass flux balanced the burning rate, resulting in a freely propagating turbulent flame front. The absence of physical surfaces in the vicinity of the flame provided free access for laser diagnostics. Stereoscopic Planar Image Velocimetry (SPIV) was applied to obtain the three components of the instantaneous velocity vectors on a vertical plane above the burner at the point of flame stabilisation. The instantaneous temperature fields were determined through Laser Induced Rayleigh (LIRay) scattering. Planar Laser Induced Fluorescence (PLIF) of acetone was used to calculate the average equivalence ratio distributions. Instantaneous turbulent burning velocities were extracted from SPIV results, while flame curvature and flame thermal thickness were calculated using the instantaneous temperature fields. The PDFs of these quantities were analysed to consider the separate influence of equivalence ratio stratification and turbulence. Increased levels of turbulence resulted in the expected higher turbulent burning velocities and flame front wrinkling. Flames characterised by higher fuel gradients showed higher turbulent burning velocities. Increased fuel concentration gradients gave rise to increased flame wrinkling, particularly when associated with positive small radius of curvature.

Design Parameters for Gasification of Maize Cobs in Throatless Gasifier

The gasification of shelled maize cobs was conducted in throatless gasifiers having 15, 22.5, 30 and 36 cm diameter reactors. The experiments were conducted with varying gas flow rate in such a way that the corresponding variation in specific gasification rate CSGR) was in the range of 120-270 kg.h-1 m-2. For each reactor, the best performance was obtained with SGR of 165 kg.h-1.m-2 The combustible gases were observed to be 31-38% of the producer gas at optimum SGR. The lower heating value of producer gas was 4.2-5.22 MJ.Nm-3. Maximum gasification efficiency obtained was 66.8-68.9% at optimum SGR. The average equivalence ratio was 0.47. The effect of diameter of reactor on efficiency of gasification was not significant, whereas the specific gasification rate (SGR) had a significant effect on gasification efficiency. The SGR value of 165 kg.h-'m2 may be used as design parameter for gasification of maize cobs in throatless gasifier.

Orifice Diameter Effects on Diesel Fuel Jet Flame Structure

The effects of orifice diameter on several aspects of diesel fuel jet flame structure were investigated in a constant-volume combustion vessel under heavy-duty direct-injection (DI) diesel engine conditions using Phillips research grade #2 diesel fuel and orifice diameters ranging from 45 μm to 180 μm. The overall flame structure was visualized with time-averaged OH chemiluminescence and soot luminosity images acquired during the quasi-steady portion of the diesel combustion event that occurs after the transient premixed burn is completed and the flame length is established. The lift-off length, defined as the farthest upstream location of high-temperature combustion, and the flame length were determined from the OH chemiluminescence images. In addition, relative changes in the amount of soot formed for various conditions were determined from the soot incandescence images. Combined with previous investigations of liquid-phase fuel penetration and spray development, the results show that air entrainment upstream of the lift-off length (relative to the amount of fuel injected) is very sensitive to orifice diameter. As orifice diameter decreases, the relative air entrainment upstream of the lift-off length increases significantly. The increased relative air entrainment results in a reduced overall average equivalence ratio in the fuel jet at the lift-off length and reduced soot luminosity downstream of the lift-off length. The reduced soot luminosity indicates that the amount of soot formed relative to the amount of fuel injected decreases with orifice diameter. The flame lengths determined from the images agree well with gas jet theory for momentum-driven nonpremixed turbulent flames.

Soot in diesel fuel jets: effects of ambient temperature, ambient density, and injection pressure

Measurements of soot distributions in fuel jets injected into high-temperature, high-pressure diesel-like operating conditions were made in an optically accessible constant-volume combustion vessel. A laser-extinction technique was used to make quantitative measurements of path-length-averaged soot volume fraction. Flame luminosity and planar laser-induced incandescence imaging were used to visualize the sooting region of the fuel jet. Flame lift-off lengths were also measured and used in the interpretation and analysis of the soot measurements. Fuel was injected with a common-rail diesel fuel injector equipped with a single 100-μm-diameter orifice. The fuel used was #2 diesel fuel. The matrix of experimental conditions included ambient gas temperatures from 850 to 1300 K, ambient gas densities from 7.3 to 30.0 kg/m 3, and injection pressures from 43 to 184 MPa. The results show that peak soot level in a fuel jet increases with increasing ambient gas temperature, with the increase scaling linearly with temperature. However, near the tip of the flame, the soot levels decrease with increasing ambient temperature, indicating significantly higher soot oxidation rates in the flame-tip region at higher temperatures. The results also show that the peak soot level in a fuel jet increases with increasing ambient gas density and decreasing injection pressure. The increase with increasing ambient density is nonlinear with respect to density. The increase with decreasing injection pressure is linear with decreasing injection velocity (or the square root of the pressure drop across the injector orifice). Overall, the trends observed in diesel fuel jet soot closely correlate with the cross-sectional average equivalence ratio at the lift-off length, with soot levels decreasing as the equivalence ratio decreases (i.e., as more air entrainment and mixing of fuel and air occur upstream of the lift-off length).

FIXED-BED GASIFICATION OF FEEDLOT MANURE AND POULTRY LITTER BIOMASS

The U.S. cattle industry is a $175 billion industry with an estimated 100 million cattle. About 10 million head ofthese cattle are in feedlots producing harvestable manure. At the same time, the U.S. poultry industry is the worlds largestproducer and exporter of poultry meat. Not surprisingly, one outcome is the production of a large quantity of manure byproducts,with approximately 60 million tons of dry harvestable animal manure produced annually from confined livestock andpoultry. This article describes a method of extracting energy from feedlot manure or poultry litter biomass either individuallyor combined with each other. High-ash (approximately 45% dry weight basis) feedlot biomass (HFB) and poultry litter biomass(HLB) were gasified in a 10 kW (thermal) fixed-bed, counter-current atmospheric pressure gasifier to generate a mixtureof combustible gases that could be further burned to generate heat. This article discusses the effect of the biomass particlesize on the composition of the product gas leaving the gasifier, the temperature profiles in the fixed bed, and the ash fusionof HFB and HLB during gasification. Air-blown gasification of the biomass fuels yielded a low-Btu gas with a higher heatingvalue of 4.4 0.4 MJ/m3 and an average product gas composition (dry basis) of H2: 5.8 1.7%, CO: 27.6 3.6%, CH4: 1.00.5%, CO2: 6.7 4.3%, and N2: 59.0 7.1%. The overall average equivalence ratio was 2.82 0.43 on a dry ash-freebasis. The experimental results also show that high-alkaline content fuels, such as HLB (Na2O + K2O = 16.7% of ash), canbe gasified by blending with lower-alkaline content fuels, such as HFB (6.0%), to reduce agglomeration in the fuel bedwithout significantly affecting the heating value of the product gas. The gasification of HLB and HFB yields a low-Btu gasthat can be combusted to generate heat for steam or power generation. The process has potential for reducing transportationcosts for traditional cropland-based manure application in some regions.

An investigation of diesel soot formation processes using micro-orifices

Soot formation processes of diesel fuel jets were investigated in a constant-volume combustion vessel under heavy-duty, direct-injection (DI) diesel engine conditions using orifice diameters as small as 50 μm. Soot was measured with line-of-sight laser extinction and planar laser-induced incandescence techniques, and flame liftoff lengths were determined with time-averaged OH chemiluminescence imaging. Results show that as fuel-air mixing upstream of the liftoff length increases, the amount of soot measured within a fuel jet decreases. When the cross-sectional average equivalence ratio at the liftoff length decreases to a value less than approximately 2, soot is no longer formed within the fuel jet. The soot measurements provide direct proof of the link between soot formation and mixing of fuel and air upstream of the liftoff length previously observed using total soot luminosity measurements. The non-sooting conditions were achieved with the 50 μm micro-orifice at an ambient gas temperature and density of 1000 K and 14,8 kg/m3 and ambient oxygen concentrations between 21% and 10%. The temperature and density are typical of DI diesel in-cylinder conditions. The lack of soot for the lower oxygen concentration conditions, which have substantially lower flame temperatures, suggests that NOx and soot can potentially be simultaneously reduced with small orifices and exhaust-gas recirculation.

95/03962 Fuels used for combined-cycle power generation

Soot formation processes of diesel fuel jets were investigated in a constant-volume combustion vessel under heavy-duty, direct-injection (DI) diesel engine conditions using orifice diameters as small as 50 μm. Soot was measured with line-of-sight laser extinction and planar laser-induced incandescence techniques, and flame liftoff lengths were determined with time-averaged OH chemiluminescence imaging. Results show that as fuel-air mixing upstream of the liftoff length increases, the amount of soot measured within a fuel jet decreases. When the cross-sectional average equivalence ratio at the liftoff length decreases to a value less than approximately 2, soot is no longer formed within the fuel jet. The soot measurements provide direct proof of the link between soot formation and mixing of fuel and air upstream of the liftoff length previously observed using total soot luminosity measurements. The non-sooting conditions were achieved with the 50 μm micro-orifice at an ambient gas temperature and density of 1000 K and 14,8 kg/m3 and ambient oxygen concentrations between 21% and 10%. The temperature and density are typical of DI diesel in-cylinder conditions. The lack of soot for the lower oxygen concentration conditions, which have substantially lower flame temperatures, suggests that NOx and soot can potentially be simultaneously reduced with small orifices and exhaust-gas recirculation.

Vehicle evaluation of neat methanol—compromises among exhaust emissions, fuel economy and driveability

Methanol was evaluated as an alternative fuel in vehicles with spark-ignited, internal-combustion engines. Acceptable driveability was achieved with a methanol-fuelled car equipped with electronic fuel injection (EFI) which was modified to provide proper air-fuel ratios for methanol. the target level for driveability was not achieved with a methanol-fuelled carburetted car modified to provide proper air-fuel ratios for and increased vaporization of methanol. With the EFI car, using the average equivalence ratio (Φa = 0·96) and spark timing designed for the production gasoline car, exhaust emissions and fuel economy with methanol fuelling were compared to those with gasoline. With methanol, compared with gasoline, 60 per cent lower NOx, 3·5 times higher unburned fuel emissions (UBF), and similar CO engine emissions were measured. the air pollution significance of the higher UBF emissions from methanol combustion is unknown because the UBF species (mainly methanol) are different from those from gasoline combustion. A catalytic converter decreased emissions of UBF and CO similarly for both fuels. Fuel economy with methanol—about half that of gasoline on a volume basis—was 7–10 per cent better on an energy basis than that with gasoline. With methanol fuelling, spark timing and Φa were varied from production values to obtain a more acceptable compromise among driveability, exhaust emissions and fuel economy. While fuelling with methanol at Φa = 0·96, using best power rather than production spark timing increased fuel economy 3 to 6 per cent without significantly affecting emissions and driveability. As Φa was leaned to 0·62 while maintaining best-power spark timing engine and tailpipe (after converter) CO emissions decreased, engine UBF emissions increased, NOx and tailpipe UBF emissions were not greatly affected, and driveability deteriorated. With best-power spark timing and the Φa for maximum economy (0·83), driveability was acceptable, and CO and NOx emissions met the 1977 standards. At Φa = 0·83, NOx emissions were reduced below the statutory standard (0·4 g/mile) by retarding spark timing; however, driveability and fuel economy deteriorated. Although the feasibility and benefits of operating vehicles with neat methanol have been demonstrated, not all problems of methanol fuelling (for example, cold start) were addressed. In addition, other alternatives such as obtaining hydrocarbon liquids from coal or using methanol as fuel for stationary powerplants must also be considered to obtain the most efficient utilization of energy resources.